10-0 SUTURES-THEIR STEREOSCAN CHARACTERISTICS Hector Maclean Melbourne University, Department of Ophthalmology

Nanette Carroll Melbourne University, Department of Ophthalmology

Summary The Scanning Electron Microscope has been used to examine a number of different sutures used in ocular microsurgery. The appearances seen in several different 10-0 materials are illustrated.

Introduction Regular users of more than one type of 1 0 4 monofilament suture are aware of differences in needle sharpness and knot holding ability. The reasons for these differences are not readily obvious under even the full power of the operating microscope.

Previous experience of scanning electron microscopy to evaluate instrument edges, and of monofilament nylon reaction in cornea(') suggested that if the technical difficulties could be overcome this would be a useful means of examination.

Materials and methods From a number of sutures the following 1 0 4 monofilament materials were examined:

Alcon 1 0 4 nylon C 4 side cutting needle. Davis & Geck 10-0 Dermalon LE-1 lancet point needle. Ethicon 1 0 4 Ethilon GS-10 micropoint spatula needle. Ethicon 10-0 Prolene GS-14 micropoint needle. Grieshaber 10-0 Tubingen nylon (black) 4 mm Barraquer needle. Morrall & Franklin 1 0 4 Perlon 5 mrn special corneal needle. Supramid 1 0 4 Supramid extra spatulated class I needle.

The needles were mounted on aluminium stubs with colloidal silver and gold coated for examination. Magnifications for the needles were standardised at x 200 for the suaged end, x 100 for the point and x 500 for the surface finish midway along the inner face. For the suture material proper, a knot was made around polyurethane foam with the suture pulled tight to assess slippage. Knots were made of three throws followed by one reverse throw in reef knot fashion. The knots were stuck to aluminium stubs with double sided adhesive tape and gold coated for examination at x 100. The suture material itself was checked for handling marks from the Birks forceps used, at a magnification at x 1000. The microscopes used were a Cambridge Stereoscan IIA and a JEOL JSM 35.

Results The findings are illustrated in the figure.

Presented at the annual meeting of the Royal Australian College of Ophthalmologists held in Singapore 1978. Address for reprints: Dr Hector Maclean, Melbourne University Department of Ophthalmology, 32 Gisborne Street, East Melbourne, Victoria 3002, Australia.

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A

C

D

E

F

I0 0 SUTCIKES THElK STEKEOSCAN CIIARA('TERIST1CS 81

Figure 1. Stereoscan appearances of 10-0 stures. All sutures shown have magnifications of:

Monofilament x 1000 Knot x 100

Point x 100 Needle polish x 500

Suage x 200

A Alcon 10-0 Nylon C 4 needle B Davis & Geck 10-0 Dermalon LE-I needle C Ethicon 10-0 Ethilon GS-10 needle D Ethicon 1 0 4 Prolene GS-14 needle E Grieshaber 10-0 Tubingen Nylon 4 mm Barraquer needle F Morrall & Franklin 10-0 Perlon 5 mm needle G Supramid 10-0 Supramid extra Spatulated Class 1 needle

Discussion The especially sharp tips of the Alcon, Davis & Geck and Grieshaber needles make for especially easy tissue entry. Some will prefer, for corneal work at least, the very short area of sharpening on the Morrall & Franklin needle. For general surface polish, the Ethilon GS-10 needle is best. The minimally less but more even smoothness of the Grieshaber needle has just as easy a passage through tissues. Roughened surfaces are not a problem for corneal work, but in corneo-scleral wounds they rapidly build up a collection of fibrin which impedes the passage of the needle through the tissues. Supramid and Prolene are the easiest to knot, possibly because they are the least smooth surfaced. Ethilon seemed to be the most slippery nylon, but the Grieshaber nylon seemed softer and held better by squashing. The Alcon, Ethilon GS-14 and Grieshaber sutures had a ratio of needle cross section area to suture cross section area of seventy to one. The remaining sutures were around one hundred to one. All sutures except the Grieshaber were crimped into the needles. We believe the Grieshaber needle has a laser drilled hole into which the nylon is affixed with a cyano-acrylate adhesive.

These remarks and the photographs should help ocular microsurgeons to choose a 10-0 monofilament suture material most suited to their particular techniques. There is still no ideal 10-0 suture material that is best in all regards.

Acknowledgements It is a pleasure to record our thanks to some of the manufacturers who made extra material available to boost our departmental range of sutures. Preparation of the photographs was in the expert hands of .I. Scrimgeour. We are grateful to Professor G. W. Crock for his encouragement for this project.

Reference 1. Haining, W. M. and Maclean, H. (1970): Scanning

electron microscopy of human cornea. Ophthalmology -Proceedings XXI International Congress, 65 1.

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